Hydrocracking petroleum and related materials by homogeneous catalysis

ABSTRACT

HIGHER MOLECULAR WEIGHT HYDROCARBONACEOUS MATERIALS CONTAINING POLYNUCLEAR SUBSTANCES, SUCH AS HEAVY PETROLEUM CRUDES AND HIGHER BOILING PETROLEUM FRACTIONS, INCLUDING RESIDUAL FRACTIONS, SHALE OIL, TAR SAND OIL, OIL AND TAR FROM COAL AND COAL ITSELF ARE HYDROCRACKED AT A ELEVATED TEMPERATURE RANGING FROM 200*C. TO 500*C. AND IN THE PRESENCE OF HYDROGEN AT A PRESSURE OF 200 TO 3000 P.S.I.G., WHILE INTIMATELY MIXED WITH A HOMOGENEOUS CONTINUOUS LIQUID PHASE CATALYST SYSTEM COMPRISING PREDOMINATELY ONE OR MORE PHOSPHORIIC ACIDS THERMALLY STABLE UNDER THE HYDROCRACKING CONDITIONS, SUCH AS PYROPHOSPHORIC ACID AND POLYPHOSPHORIC ACIDS HAVING AN EMPIRICAL RATIO OF H2O:P2O5 OF 3 OR LESS, AND MINOR PROPORTION, E.G., LESS THAN 20% BY WEIGHT OF CERTAIN IODINE COMPOUNDS, E.G., SPECIALLY HL, OR NH4L.

United States Patent U.S. Cl. 208-108 Claims ABSTRACT OF THE DISCLOSURE Higher molecular weight hydrocarbonaceous materials containing polynuclear substances, such as heavy petroleum crudes and higher boiling petroleum fractions, including residual fractions, shale oil, tar sand oil, oil and tar from coal and coal itself are hydrocracked at an elevated temperature ranging from 200 C. to 500 C. and in the presence of hydrogen at a pressure of 200 to 3000 p.s.i.g., while intimately mixed with a homogeneous continuous liquid phase catalyst system comprising predominately one or more phosphoric acids thermally stable under the hydrocracking conditions, such as pyrophosphoric acid and polyphosphoric acids having an empirical ratio of H O:P O of 3 or less, and a minor proportion, e.g., less than 20% by weight of certain iodine compounds, e.g., specially HI, NaI or NH I.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to the catalytic hydrocracking of higher boiling petroleum oils, shale oil, tar sand oil, coal and oil from coal in the presence of certain iodine compounds.

Description of Prior Art It is known that coal tars and similar materials can be hydrocracked in the presence of mixturues of elemental iodine and HI. Such a process is described, for example, in US. 3,453,202 to Friedman et al. It is also known from US. 3,355,376, 3,371,049, 3,594,329 and 3,625,861 that various hydrocarbonaceous materials such as heavy petroleum oils, tar sand oils, shale oil, coal and coal extracts can be hydrocracked in the presence of polyvalent metal halides, and from US. 3,677,932 that the catalytic activity of certain polyvalent metal halides can be promoted by the addition of small amounts of a mineral acid, preferably corresponding hydrogen halides and pyrophosphoric acid.

While there are various advantages obtainable by the use of I /HI or polyvalent metal halide catalysts for the hydrocracking of heavy hydrocarbonaceous materials there are still many obstacles to commercialization of such processes as Will be apparent from the many publications in this field, including the aforementioned patents.

SUMMARY OF THE INVENTION It has now been found that there are still further advantages obtainable in the use of HI and other iodine compounds such as NH I and alkali metal iodides as hydrocracking catalysts, by use of said iodine compounds in admixture or dissolved in a relatively large proportion of molten pyrophosphoric acid as a medium for carrying out the hydrocracking. By pyrophosphoric acid as employed in the specification and claims, is meant H P O or the equilibrium mixtures of ortho, pyroand polyphosphoric acids corresponding empirically thereto, or other mixtures of the various phosphoric acids in which the substance is represented by the average formula nH O /P O wherein n has a positive value 3 or less and the mixture contains a substantial amount of molecular species wherein m is from 1 to 2, inclusive. The compositions and physical 3,824,179 Patented July 16, 1974 properties of such phosphoric acid mixtures are described in Encyclopedia of Chemical Technology, by Kirk and Othmer, 2nd Edition, 1968, Vol. 15, pages 241 and 242. This invention is based on the discovery that molten pyrophosphoric acid at 200 to 500 C. is uniquely useful as a medium for hydrocracking petroleum oils, shale oils, tars and oils, coal oils and coal in the presence of an effecttive, relatively small amount of certain iodine compounds such as HI, which is known to be useful as a hydrocracking catalyst for such materials. By practice of the invention it is possible to achieve very high rates of hydrogenation even at low iodine concentrations. Moreover, a very desirable product distribution with relatively high yields of high boiling range hydrocarbons, as compared to less desirable CH C H hydrocarbons, can be obtained. Pyrophosphoric acid, as distinguished from sulfuric and other oxidizing acids, is advantageous in that it is not reduced by hydrogen or hydrocarbonaceous feeds or products, nor is it adversely affected by nitrogen, sulfur or oxygen products of the conversion. As an essentially non-oxidizing substance, pyrophosphoric acid is compatible with the iodine catalysts and the hydrocarbonaceous feeds without promoting their oxidation. It also provides an acidic medium which allows mild cracking while obtaing efiicient catalytic hydrogenation of the cracked fragments and other hydrogenable uncracked substances which makes it feasible to use a smaller proportion of a given catalytic iodine compound. It also provides a system in which the acid function-catalyzed reactions and catalyzed hydrogenation can be controlled or regulated with a greater degree of independence from one another.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is praticed by intimately contacting a hydrocarbonaceous feed with hydrogen in a continuous phase molten mixture predominating .in pyrophosphoric acid containing a minor proportion of certain iodine compounds as catalyst under hydrocracking conditions, including a temperature in the range from 200 C. to 500 C., preferably from 300 to 400 C., and a pressure of at least 200 p.s.i.g., e.g., from 200 to 3000 p.s.i.g., preferably 1500 to 2500 p.s.i.g. Hydrocarbonaceous feeds which can be suitably processed include, for example, heavy oils and residues, coal, coal extracts, shale oil and the like.

The process can be carried out batchwise or continuously. Contacting of the charge material, catalyst and pyrophosphoric acid medium can be effected by various methods and means, including co-current and counter-current contacting. The reaction components can be introduced into the hydrocracking zone separately, or two or more of the reaction components can be pre-mixed before subjecting them to hydrocracking.

In one embodiment of the invention, the charge material and hydrogen are continuously delivered to a body of the liquid pyrophosphoric acid and iodine catalyst and the reaction products are continuously withdrawn in gaseous form and separated from the unconverted hydrogen and iodine which are recyled to the reaction zone. A portion of the organic material can also be recycled for further conversion if desired.

Exothermic heat of reaction can be removed as heat of vaporization or sensible heat of the gaseous and vaporous stream, and/or by providing suitable internal or external heat exchange between the hot liquid reaction medium and a suitable coolant to maintain the desired temperature in the reaction zone.

A slip-stream can be continuously withdrawn from the reaction zone and filtered or centrifuged to remove solid contaminants, such as carbon and ash, and the separated liquid phase returned to the reaction zone. Accumulated tarry material in the reaction mixture may be removed by taking a slip-stream of the reactant mixture and extracting it with a suitable solvent such as a C to C aromatic hydrocarbon.

Make-up pyrophosphoric acid and iodine catalyst can be added as required. The make-up acid can be provided by adding orthophosphoric acid to the reaction zone wherein it loses water at the elevated temperature to form pyrophosphoric acid, the excess water (regardless of source) being evolved with the volatile reaction products. Alternatively, or simultaneously, phosphorus pentoxide can be added which reacts with water derived from orthophosphoric acid, or uncombined water in the charge, or water resulting from conversion of bound oxygen in the feed with hydrogen. Make-up iodide can be supplied directly to the reaction zone as such, either as solid or molten material, or it can be pre-mixed with make-up pyrophosphoric acid or carbonaceous feed.

The catalytic system in accordance with the invention is a continuous phase liquid composed predominately of pyrophosphoric acid and a minor proportion, generally from about 1% by weight to about 20% by weight, preferably from 2% to 10% by weight, of an iodine com pound selected from the group consisting of HI, NH I, and alkali metal iodides, particularly NaI. Elemental iodine will also normally be present in the reaction zone in equilibrium with the iodine compounds dissolved in the pyrophosphoric acid. Iodine may in fact be employed as a convenent source of HI, i.e., iodine can be reacted with hydrogen to form the required concentration of HI in the pyrophosphoric acid. Because hydrocracking is effected using a relatively inexpensive iodide/pyrophosphoric acid catalyst which need not contain any expensive metals, the present process is advantageous in that no metal recovery is required.

The extent to which the hydrocracking charge dissolves in or reacts with the catalyst system depends in part on the oxygen, nitrogen and sulfur contents of the charge. Petroleum oils low in these elements are relatively insoluble resulting in a heterogeneous reaction mixture. On the other hand, coal, coal extracts and shale oil which con tain larger proportions of such polar atoms are more soluble in the highly polar pyrophosphoric acid.

The method of practicing the invention and the results obtained thereby are illustrated by the following examples.

A series of experiments were conducted in which coal was hydrocracked in pyrophosphoric acid alone (Experiment 1), in a bulk iodine/HI system (Experiment 2) and in pyrophosphoric acid containing various iodine compounds in accordance with the invention (Experiments 3-4). The hydrocracking conditions and composition of the respective catalyst systems and the products obtained from hydrocracking are shown in the following table. The hydrocracked products are reported in units of grams per 100 g. of moisture and ash-free (MAF) coal.

TABLE A Experiment 1 2 3 4 Catalyst type Amount, g..- HiP207, g Temperature,

CaHu MOP (methyl cyclpentane) 07H plus CsHm CoHzo to 250 C. boiling range hydrocarbons 4 9 Total CAHm to 250 C. boiling range hydrocarbons 0. 1 20. 4 Hz consumed, g./100 g. MAF coal---" 1.5 9 Max mum rate of Hz uptake, p.s.i.g./

I Big Horn coal (moisture free, 100-200 mesh, 6.5% ash). b Tr=trace.

* None.

, The results of Experiments 3 and 4 indicate that relatively high rates of hydrogenation can be achieved by use of the catalyst system in accordance with the invention at relatively low catalyst concentrations. The results obtained also indicate that relatively good yields of C H to 250 C. boiling range hydrocarbons are produced as compared to less desirable CH --C H hydrocarbons. In addition, the iodide/pyrophosphoric acid system of the invention produces a soluble tar, high in hydrogen content and low in heteroatoms, which is also highly advantageous.

The advantageous hydrogenation activity of the present iodide/pyrophosphoric acid system was demonstrated in a further set of experiments wherein the time of the run was reduced from 30 minutes at 365 C. (Experiment 5) to only 2.5 minutes at 320 C. (Experiment 6). The results of these experiments are shown in Table B.

TABLE B Experiment 5 6 NH4I N H4I 5. 0 5. 0 150 150 Temperature, 0.. 365 320 Time at temperature, min 30 2. 5 Products, g./100 g. MAF coal:

CO: 2. 7 0. 8 CH3-C3H3 1. 1 O. 3 C4H10 1. 2 O. 4 C5Hu82 C. boiling range hydrocarbo 2. 9 0.5 82-160 0. boiling range hydrocarbons 6. 1 1. 0 l60271 C. boiling range hydrocarb0ns 7. 9 1. 9 271 0. plus boiling range hydrocarbons 7. 8 1. 1 H2 consumed, g./100 g. MAF coal 5. 4 3.3 Conversion of carbon, percent:

Voltaile products 32. 3 6. 5 Non-extractable 0. percent 1. 0 29.0 Extractnblc tar (by difference 67 64 The foregoing results indicate that although total conversion fell oif somewhat at the reduced time and temperature, the amount of extractable tar product produced was approximately the same for both runs. Moreover, as in the previous experiments, the tar was found to have a relatively low sulfur content (because of hydrogenation of sulfur compounds in coal to H 8), which demonstrates the suitability of the present iodide/pyrophosphoric acid system for producing a low sulfur fuel oil from a high sulfur content coal.

What is claimed is:

1. In a process for hydrocracking higher molecular weight hydrocarbonaceous materials containing polynuclear substances by contacting said materials in the presence of hydrogen with a continuous liquid phase catalyst system containing HI, NH I or an alkali metal iodide as the essential hydrocracking catalyst under hydrocracking conditions including a temperature in the range of 200 C. to 500 C. and a pressure of from 200 to 3000 p.s.i.g., the improvement which comprises providing said catalyst in homogeneous liquid phase mixture with a major proportion of at least by weight of pyrophosphoric acid.

2. The process of claim 1 wherein the catalyst system consists essentially of 1-20% HI dissolved or in admixture with at least 80% by weight of pyrophosphoric acid.

3. The process of claim 1 wherein the catalyst system is essentially 120% by weight NH I dissolved or in admixture with at least 80% by weight pyrophosphoric acid.

4. The process of claim 1 wherein the catalyst system consists essentially of 1-20% by weight NaI dissolved or in admixture with at least 80% by weight pyrophosphoric acid.

5. The process of claim 2 wherein the concentration of H1 is from 2 to 10% by weight.

(References 011 following page) 5 6 References Cited FOREIGN PATENTS UNITED STATES PATENTS 70/ 10318 1/ 1971 Netherlands 208--108 1 9 7 i et 1 2,034,693 Germany 208108 2/1940 Pier et a1 20810 3/1937 Dreyfus 5 DELBERT E. GANTZ, Pnmary Examlner 2/1968 Gorin et a1. 252'413 G. E. SCHMITKONS, Assistant Examiner 7/1969 Friedman et a1. 208-40 3/1972 Dengler et a1. 208-10 7/1973 Schuman 612211 208--10 10 20810;252435 10/1973 Kiovsky 208--10 

